We are requesting support for a Clinical Core Unit to coordinate the acquisition of crucially needed tissue specimens (blood samples, muscle biopsies, skin and muscle cultures, postmortem brain) from patients with the rara disorders studies in the three projects. This Core takes advantage of one of the great strengths of the Center, which has been for many years a major referral center for the diagnosis of neuromuscular disorders, especially mitochondrial encephalomyopathies. Investigators in the Clinical Core will participate in the identification of patients, their accurate clinical and scientific workup, and in the collection of adequate samples. Partial salary support is requested for the Core Director and for a Technical Assistant. Technical needs include service contracts for some instruments used in the diagnostic workup of patients and for liquid nitrogen.